When a capacitive touch panel is applied to a large scale device, a number of sensing lines is increasing. Furthermore, requirements for accelerating sensing speed and calculating scan results are also increasing.
In an axis intersect (AI) capacitance sense technology, a coordinate of a touch is detected by a self-capacitance sensing method. However, a problem of ghost point occurs in the AI capacitance sense technology. As a result, a multi-point touch cannot be detected. In contrast, in an all-points addressable (APA) capacitance sense technology, a coordinate of a touch is usually detected by a mutual-capacitance sensing method. Accordingly, a multi-point touch can be detected in the APA capacitance sense technology.
A capacitive touch device comprises a touch panel, a plurality of touch integrated circuits (IC) and a processing unit. Currently, there are two methods to calculate a coordinate of a touch. In a first method, the touch ICs scan the touch panel for obtaining sensed data and calculates the coordinate of the touch according to the sensed data. After the coordinate of the touch is calculated, the coordinate of the touch is transmitted to the processing unit. In a second method, because the arithmetic capability of the processing unit is better than that of the touch ICs, and the coordinate of the touch is calculated by the processing unit to increase the speed of obtaining the coordinate of the touch. More particularly, the touch ICs scan the touch panel for obtaining the sensed data. Then, the touch ICs transmit the sensed data to the processing unit, and the processing unit calculates the coordinate of the touch according to the sensed data. In summary, the touch ICs transmits the coordinate of the touch to the processing unit in the first method, while the touch ICs transmits the sensed data to the processing unit in the second method. A quantity of the sensed data is large than a quantity of the coordinate of the touch. Accordingly, time for transmitting the sensed data is more than time for transmitting the coordinate of the touch especially when the capacitive touch device adopts the all-points addressable (APA) capacitance sense technology. Furthermore, power consumption is increasing when the large amount of the sensed data is transmitted to the processing unit.
Therefore, there is a need for a solution to solve the above-mentioned problem that the quantity of the sensed data is large when the touch ICs transmit the sensed data to the processing unit.